A Request for Changes to the Controlled Area Boundary
Southern California Edison in December filed a request for an exemption with the Nuclear Regulatory Commission to slightly reduce the Controlled Area Boundary that surrounds the dry fuel storage system at the San Onofre Nuclear Generating Station (SONGS), which is also known as the independent spent fuel storage installation, or ISFSI.
This controlled area, according to the NRC, sets dose limits for the public and the “minimum distance from the spent fuel, high-level radioactive waste, or reactor-related GTCC waste handling and storage facilities to the nearest boundary of the controlled area must be at least 100 meters.” SCE is requesting an exemption to the 100 meter standard.
Instead, SCE proposes to establish the ISFSI CAB at or within the site boundary, essentially the fence line, which is roughly 40 meters from the closest storage canister.
The changes are part of an effort to bring two separate NRC boundaries in line with the current state of SONGS, which is: no operating reactors and all fuel in dry storage. Besides the CAB, there is also an Exclusion Area Boundary, a wider ring, that is likewise geared toward a site with an operating reactor. For certain postulated events while the reactors were operating, both these boundaries would allow SCE to remove people or property from the area.
“With all the nuclear fuel in dry storage, those types of accident scenarios just don’t exist anymore,” said Ron Pontes, SCE general manager for environment and radiation protection. “There are no design basis accidents that can result in an off-site dose that exceeds safe regulatory limits, so reducing the CAB in the interest of continued public access seems appropriate.”
Relatedly, limiting the Exclusion Area Boundary was a request of the California State Lands Commission in a lease provision approved in 2019. To comply with the provision, SCE will separately pursue the elimination of the EAB through the NRC’s 10 CFR 50.59 process.
The reduction allows SCE to relinquish explicit control of areas beyond the site boundary during both normal operations and post-accident conditions and at the same time maintain radiation dose to an individual well below safe regulatory limits.
As part of the dose analysis included with the submittal to the NRC, SCE reported that standing outside the proposed CAB line for 300 hours a year would result in a dose of 0.60 millirem a year. Everybody receives about 620 mrem a year in radiation dose from natural and man-made sources. The NRC standard for whole-body dose to a member of the public is 25 mrem a year.
“Making the changes to both the CAB and the EAB are, at the end of the day, administrative measures, so the public should not notice any differences as they go out and use the local beaches,” Pontes said.
There are no changes to any physical barriers surrounding the SONGS site as part of this request, nor does the change to the EAB affect the site’s emergency planning.
(Posted Jan. 14, 2022)